Interpretive Summary: It is unknown if increases in atmospheric CO2 concentration will impact loss of soil in agricultural systems. Following a 10 year study examining the effects of elevated CO2 in two cropping systems (conventional tillage and no-till), we investigated sediment loss using simulated rainfall. Both systems included a grain sorghum and soybean rotation. The no-till system also included crimson clover, sunn hemp and wheat as winter cover crops. Soil surface residue was increased by high CO2, especially in the no-till system. The higher residue under no-till increased water infiltration. Loss of soil was low under no-tillage regardless of CO2 level, but elevated CO2 did decrease soil loss only under conventional tillage. Findings suggest that both high CO2 and no-tillage increased surface residues which can improve water infiltration and reduce soil loss.

Technical Abstract:
No work has investigated whether increasing atmospheric CO2 concentration will impact sediment loss in agricultural systems. Rainfall simulation was conducted following a 10-year study investigating the effects of atmospheric CO2 level (ambient and twice ambient) in two cropping systems (conventional tillage and no-tillage) on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional system consisted of a sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.] rotation using spring tillage and winter fallow. The no-tillage system used this rotation along with three rotated cover crops [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)] without tillage. Elevated CO2 increased residue in both tillage treatments, with the effect being greater under no-tillage. This resulted in increased water infiltration only under no-tillage. Overall, sediment loss was low under no-tillage regardless of CO2 level; therefore, elevated CO2 decreased sediment loss only under conventional tillage. Our results showed that both high CO2 and no-tillage increased surface residues; this can improve water infiltration and reduce soil loss.